Richard Dawkins called it “the curse of the discontinuous mind” – our tendency to lump things into discrete categories. Nowhere is this more apparent than in our perception of ethnic races, which we tend to see as reflecting absolute dividing lines in the human population. Do mistaken folk beliefs about genetics play a role in this? A new study by Jason Plaks and his team suggests so. What’s more, their findings have interesting implications for an anti-prejudice intervention based around genetics lessons.

The background to this work is that people often mistakenly assume that superficial ethnic characteristics are a reliable sign of significant genetic difference. In fact, each of us is about 99.9 per cent similar genetically to the next person. And the genetic variability that does exist in the human race tends to be greater within ethnic groups than between them.

Plaks and his colleagues devised an ingenious memory test to expose the tendency of their 84 student participants to see black and white races as clear-cut categories (the students were from various ethnic backgrounds, but the majority were white). The stimuli were faces morphed from real photos of black and white people to consist of seven degrees of prototypical blackness and whiteness (including: all black, all white, 50/50, 16.67 per cent black, 16.67 per cent white, 33.33 per cent black and 33.3 per cent white).

These faces appeared in sequence on-screen interspersed with numbers. The participants’ task for each number and each face was to say whether it was the same as the last seen number or face. For people who see ethnic races as distinct categories, the racial profile of the faces ought to have interfered with their memory performance. That’s exactly what was found.

After the task, the participants were asked how much genetic overlap two random people on earth would be expected to have (the average answer was 56 per cent). Those participants who said there would be less overlap tended to be the same ones who were affected by the racial profile of the faces. That is, they were more likely to say mistakenly that the current face was the same as the last face, if the two faces had a similar racial profile. This suggests they were using racial cues to remember the faces. By contrast, participants who believed there is more genetic overlap between strangers tended to be unaffected by the racial profile of the faces. Presumably they used more idiosyncratic features of the faces to remember them by.

If belief in genetic variation is correlated with people’s tendency to categorise faces according to race, then what if people are educated about human genetic variation – might that change their proclivity for prejudice? The next stage of the Plaks’ study suggested so.

Half of 95 participants read a passage of text (adapted from a real American Psychologist article) that correctly stated the 99.9 per cent genetic overlap between random individuals, and drew an analogy between ethnic groups and social clubs. The other half of the participants read a version that said genetic overlap between individuals is low (21.4 per cent) and drew an analogy between ethnic groups and families. Again, the participants were from various ethnic backgrounds, but most were white.

Afterwards the participants had to rate words (e.g. “disgusting”, “delightful”) as either positive or negative as fast as they could. A crucial twist was that the words were preceded by a face prime with varying degrees of racial black or whiteness. For the participants who read the low genetic overlap text, the racial profile of the face prime made a difference – they were quicker to categorise negative words after a face that was 25 per cent black or more. By contrast, the racial profile of the face primes made no difference to the performance of the participants who read the text explaining the high genetic overlap between humans. In other words, being educated about the genetic overlap between humans seemed to reduce participants’ sensitivity to, and discrete categorisation of, racial colour, thereby reducing their implicit prejudice in the word recognition task.

Plaks and his colleagues said this result suggests people’s beliefs about genetic variation are malleable and could therefore be a useful target for anti-prejudice interventions. “People without a strong motivation for prejudice – and even those with professed egalitarian ideals – frequently display signs of racial stereotyping,” the researchers concluded. “We suggest that people with egalitarian ideals may still exhibit stereotyping at least partly because they harbour particular assumptions about genetic variation.”_________________________________

It's just possible that this work may also be influenced by exposure to different faces in first 6 months of life. I can't quite put finger on it, but recent tweet, re. Monkeys' able to differentiate human faces, linked with brain plasticity work with babies suggests this may be relevant. If I find the ref. will comment again. CBS

AbstractExperience plays a crucial role for the normal development of many perceptual and cognitive functions, such as speech perception. For example, between 6 and 10 months of age, the infant's ability to discriminate among native speech sounds improves, whereas the ability to discriminate among foreign speech sounds declines. However, a recent investigation suggests that some experience with nonnative languages from 9 months of age facilitates the maintenance of this ability at 12 months. Nelson has suggested that the systems underlying face processing may be similarly sculpted by experience with different kinds of faces. In the current investigation, we demonstrate that, in human infants between 6 and 9 months of age, exposure to nonnative faces, in this case, faces of Barbary macaques (Macaca sylvanus), facilitates the discrimination of monkey faces, an ability that is otherwise lost around 9 months of age. These data support, and further elucidate, the role of early experience in the development of face processing. CBS GreatMindsHeart@twitter http://healthyminds.blog.com

I can't access the original paper, so can't see if this was addressed, but the 99.9 per cent figure seems to be dropping. The 99.9 per cent was based on SNPs. Estimates now that a couple of genomes have been fully sequenced are in the range of 98 to 99 per cent – which is the range that we used to say was the difference between chimpanzees and humans (I think estimates of that similarity is now around 95-96 per cent).

Yeah, I'm really not sure about that 99.9% value for genetic similarity. It depends on which markers you use when comparing populations…there are ways to identify ancestry using SNP's from “junk” DNA [HUMAN MUTATION 29(5),648-658,2008], while the protein-coding regions of DNA are almost entirely conserved. Additionally, chimpanzees have 48 chromosomes and humans have 46…how can you quantify this difference? Just as race really cannot be quantified or delineated, one's genetic similarity to another human or even to a chimp cannot be generalized and quantified. We shouldn't have to put a number on “almost identical”. Putting a number on such a thing is about the same as creating a dividing racial line that doesn't really exist.

The “greater variation within groups than between them” statement is also iffy. This applies to examples where group differences with genetic roots are observable, variation in height between people of European and Chinese origin for one.

How would this knowledge stop people using visible racial characteristics to identify people?

So when people of limited early exposure say they have trouble 'telling them apart' there is some truth to it other than a racist world view? The apparatus in the brains for varied facial recognition was subsumed for other brain functionality?